Our game "ToyBorgs"

i almost forgot to inform you about our game that was released 2 months ago. It's called ToyBorgs and uses farseer physics. It supports local and online matches through Xbox LIVE and we are currently adding a singleplayer mode:

During the video showing the particle editor, at about 1:22 you change the "Type" to something and then it creates some kind of very interesting vortex effect. Could you explain that a little bit more? What was that and do you have any tips for
implementing it in something else? Is it a pixel shader perhaps?

During the video showing the particle editor, at about 1:22 you change the "Type" to something and then it creates some kind of very interesting vortex effect. Could you explain that a little bit more? What was that and do you have any tips for
implementing it in something else? Is it a pixel shader perhaps?

Yes, it is a pixel shader and is using a texture map rendertarget to determine what pixels are distorted. At the beginning of each render loop the map is cleared with black. All particle emitters whos type is "refraction" render their particles
onto this rendertarget. The pixel shader then does the refraction and only refracts pixels that have a color brighter than black. The brighter the pixel is, the more it gets distorted. This way you can easily create some cool effects by using the editor rather
then writing code for it.

Thanks, I appreciate your response. I guess this is about the time where I go and start learning and experimenting with pixel shaders. I know it may be asking too much but I would however love to know what algorithm in your pixel shader you used to create
that circular vortex. Did you play with values and formula's till you got the desired output or use a math formula you already knew about? I'm currently in college so one of my questions is what math I should be taking to possibly gain knowledge in these areas.